Sheet size detecting device

ABSTRACT

A sheet size detecting device is provided with the following a tray in which sheets are stored, guides that can be adjusted in position in accordance with the size of sheets stored in the tray, and bit generation sections that are moved in synchronism with movement of the guides. The device detects bits based on the movement of the bit generation sections, and the number of bits detectable is larger than the number of bit generation sections by at least one. The device detects the size of sheets stored in the tray on the basis of the correspondence between the combination of detected bits and the sizes of sheets which can be stored in the tray.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. application Ser. No.10/383,677, filed Mar. 10, 2003, the entire contents of which areincorporated herein by reference.

This application is based upon and claims the benefit of priority fromthe prior Japanese Patent Application No. 2002-097552, filed Mar. 29,2002, the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a sheet size detecting device fordetecting the size of sheets stored in a position.

2. Description of the Related Art

Copying machines, printers or facsimile machines have a function ofdetecting the size of sheets stored in a predetermined position. Thesheet size detection is realized by optical sensors that are selected orused in accordance with the size of sheets. The sensors are made todetect a sheet, for example when a platen cover is closed.

Jpn. Pat. Appln. KOKAI Publication No. 6-64781 discloses a technologywherein eight sheet sizes are detected by use of three sensors.According to this publication, the sheet sizes are detected by providingguides that can be adjusted in position in accordance with a size of asheet, providing three code plates that are movable in synchronism withthe guides, and arranging three sensors that detect the code plates,respectively. When sheets are stored in a tray and the guides are movedin accordance with the sheet size, a check is made to see whether or notthe three sensors detect the corresponding code plates, and the sheetsize is detected based on this check. To be more specific, the sheetsize detection is performed as follows. For example, when the codeplates are adjusted in position to increase the size from “size 1” to“size 8” in turn, a check is made to see whether the sensors detect thesheets. The detected states of the sensors are determined by comparingthe detection signals with eight bit combination patterns, which aredetermined beforehand and correspond to different bit information ofdifferent sheet sizes.

Since the sheet size detecting device employs sensors in accordance withthe number of sheet types, a large number of sensors are required. Forexample, if the sheet size detecting device detects eight types ofsheets, eight sensors are required. Due to the necessity of using alarge number of sensors, the sheet size detecting device is inevitablylarge in size and costly.

In the sheet size detecting method of Jpn. Pat. Appln. KOKAI PublicationNo. 6-64781, three code plates and three sensors are required fordetecting eight sheet sizes. That is, the bit generation means and thebit detection means must be equal in number.

BRIEF SUMMARY OF THE INVENTION

Accordingly, an object of the present invention is to provide a sheetsize detecting device which can detect sheet sizes by means of a compactstructure, and which can be provided at low cost.

A sheet size detecting device according to one aspect of the presentinvention comprises: a tray in which sheets are stored; guides that canbe adjusted in position in accordance with the size of sheets stored inthe tray; and bit generation sections that are moved in synchronism withmovement of the guides. The device detects bits based on the movement ofthe bit generation sections, and the number of bits detectable is largerthan the number of bit generation sections by at least one. The devicedetects the size of sheets stored in the tray based on thecorrespondence between the combination of detected bits and the sizes ofsheets that can be stored in the tray.

Additional objects and advantages of the invention will be set forth inthe description which follows, and in part will be obvious from thedescription, or may be learned by practice of the invention. The objectsand advantages of the invention may be realized and obtained by means ofthe instrumentalities and combinations particularly pointed outhereinafter.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate embodiments of the invention, andtogether with the general description given above and the detaileddescription of the embodiments given below, serve to explain theprinciples of the invention.

FIG. 1 shows the outward appearance of a tray according to oneembodiment of the present invention, as well as part of the internalstructure of the tray.

FIG. 2 shows a sheet size detecting mechanism.

FIG. 3 is a schematic diagram showing a cross section of a bit detectingmechanism.

FIG. 4 illustrates how sheet sizes are detected.

FIG. 5 is a schematic diagram showing a control block of a sheet sizedetecting device.

FIG. 6 is a table illustrating the correspondence between detected bitpatterns and sheet sizes.

FIG. 7 is a schematic diagram showing how a sheet size is detectedaccording to the second embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

One embodiment of the present invention will now be described withreference to the accompanying drawings. In the embodiment, a sheet sizedetecting device 2 is provided for the manual insertion tray 11 of acopying machine 1 shown in FIG. 5.

(First Embodiment)

FIG. 1 shows the outward appearance of the manual insertion tray 11 aswell as part of the internal structure of the tray 11. The tray 11 hastwo guides 12 and 13 each having a substantially “L”-shaped crosssection. The guides 12 and 13 are movable in the longitudinal directionof the tray 11 in accordance with the size of sheets to be used. Each ofthe L-shaped guides is made up of two plates, one plate being parallelto the manual insertion tray 11, and the other plate being perpendicularthereto. Sheets are stored between the plates that are perpendicular tothe manual insertion tray 11.

Guide 12 is integrally assembled with a rack gear 14. The rack gear 14is in mesh with a pinion gear 16 which is rotatable around an axisperpendicular to the moving direction of the guide 12. Likewise, guide13 is integrally assembled with a rack gear 15. This rack gear 15 isalso in mesh with the pinion gear 16 and extends in parallel to the rackgear 14 described above. With this structure, when one of the guides 12and 13 is moved in accordance with a sheet size, the other guide move inthe opposite direction simultaneously. Therefore, the center of thesheets is always at the same position without reference to the sizes ofthe sheets, i.e., without reference to the adjustment of guides 12 and13.

Sheets of eight sizes “A” to “H” can be stored in the manual insertiontray 11. The sheet size increases from size “A” to size “H” in thisorder.

FIG. 2 shows a mechanism for detecting a sheet size when sheets arestored in the manual insertion tray 11 and the guides are adjusted inaccordance with the size of the sheets. It should be noted that FIG. 2shows the sides of the pinion gear 16, rack gear 14 and rack gear 15that are opposite to the sides shown in FIG. 1. In other words, thepinion gear 16, rack gear 14 and rack gear 15 shown in FIG. 1 aredepicted upside down in FIG. 2. The plate of guide 12 that is parallelto the manual insertion tray 11 is fixed to one end of rack gear 14 bymeans of bolts 17, and the plate of guide 13 that is parallel to themanual insertion tray 11 is fixed to one end of rack gear 15 by means ofbolts 18. With this structure, guides 12 and 13 are integrally assembledwith rack gears 14 and 15, respectively. The rack gears 14 and 15 areopposed to each other and in mesh with the pinion gear 16 locatedtherebetween.

The rack gear 15 has bit generating sections 19 and 20 to determine theguide positions. The bit generating section 19 has a rectangularprojected portion extending in the moving direction of the guide 13. Adepressed portion (a hollow section) 21 is located at the predeterminedposition of the projected portion. Likewise, the bit generating section20 has a rectangular projected portion extending in the moving directionof the guide 13.

Electric switches made up of stationary metal terminals and conductiveelastic members and serving as bit detecting sections are located atpositions to which the bit generating sections 19 and 20 of the rackgear 15 are movable. As shown in FIG. 2, the stationary metal terminals22, 23 and 24 are prevented from moving together with the rack gear 15.To be more specific, they are fixed inside the manual insertion tray 11.They are supported by means of support members, for example. Two (22,23) of the stationary metal terminals are provided at positions to whichbit generating section 19 is movable, and the remaining one (24) isprovided at a position to which bit generating section 20 is movable.

The elastic conductive members 25, 26 and 27 are located between thestationary metal terminals 22, 23 and 24 and the moving tracks of thebit generating sections 19 and 20. One-end portions of the conductiveelastic members 25, 26 and 27 are secured inside the manual insertiontray 11. When the bit generating sections 19 and 20 move and theprojected portions come to predetermined positions, one end ofconductive elastic member 25 comes into contact with stationary metalterminal 22. A bit is detectable in this electrically conductive state.Therefore, the conductive elastic member and the stationary metalterminal jointly function as an electric switch. Bit detection signalsfrom the three electric switches are supplied to ports X, Y and Z,respectively, and these ports are formed in the sheet size detectingsection 3 that is provided for the sheet size detecting device 2, asshown in FIG. 5.

FIG. 3 is a schematic diagram showing a cross section of a mechanismthat is configured to detect a bit when the electric switch is turnedon.

The bit generating section 19, which is integral with the rack gear 15,moves in the direction indicated by the arrow in FIG. 3, in synchronismwith the movement of the guide 13. The stationary metal terminal 22 andthe conductive elastic member 25 are located at positions toward whichthe bit generating section 19 moves.

The conductive elastic member 25 has a cross section substantially inthe shape of “S.” When the bit generating section 19 moves, itsprojected portion raises the concave portion 28 of the conductiveelastic member 25 (i.e., the concave portion 28 is moved in the upwarddirection as viewed in FIG. 3). When the concave portion 28 of theconductive elastic member 25 is raised, the convex portion 29 of theconductive elastic member 25 is raised as well and brought into contactwith the stationary metal terminal 22. When the conductive elasticmember 25 and the stationary metal terminal 22 are in contact with eachother, a current is allowed to flow, and the electric switch 30 detectsa bit.

When the rack gear 15 moves further, the depressed portion of the bitgenerating section 19 comes to the position of the concave portion 28 ofthe conductive elastic member 25. At this time, the conductive elasticmember 25 returns to its original position because of the elasticitythereof. Since the conductive elastic member 25 is separated from thestationary metal terminal 22, the electric switch 30 no longer detects abit.

As can be seen from the above, the movement of the bit generatingsection 19 provided with the depressed portion 21 at the predeterminedposition allows detection of four bit combination patterns, namely, thepatterns determined by whether or not electric switch 30 (made up ofstationary metal terminal 22 and conductive elastic member 25) detects abit and by whether or not electric switch 31 (made up of stationarymetal terminal 23 and conductive elastic member 26) detects a bit. Inaddition, the movement of the bit generating section 20 allows detectionof two bit combination patterns, namely, the patterns determined bywhether or not electric switch 32 (made up of stationary metal terminal24 and conductive elastic member 27) detects a bit. Hence, the manualinsertion tray 11 can detect eight sheet sizes.

FIG. 4 illustrates how the sheet sizes are detected based on bitsdetected by the electric switches 30, 31 and 32.

In FIG. 4, the numbers within the thick-line frames indicate bitinformation which the electric switches 30, 31 and 32 output when theguides 12 and 13 are moved in accordance with the sheets of sizes A to Hand the rack gear 15 moves accordingly. The bit detected by electricswitch 30 is output to port X, the bit detected by electric switch 31 isoutput to port Y, and the bit detected by electric switch 32 is outputto port Z.

When the guides 12 and 13 are adjusted to the positions of size A (inwhich case, sheets have the narrowest width), “0”, “0” and “1” areoutput to ports X, Y and Z. The bit information detected by the electricswitches 30, 31 and 32 changes each time sheets of a different size areused. The bits output to ports X, Y and Z are “0,1,1” in the case ofsize B, “0,1,0” in the case of size C, “1,0,1” in the case of size D,“1,1,1” in the case of size E, “1,1,0” in the case of size F, “1,0,0” inthe case of size G, and “0,0,0” in the case of size H.

As described above, when the guides 12 and 13 adjusted in accordancewith the sizes of sheets, the electric switches 30, 31 and 32 outputeight kinds of bit information dependent on the sheet sizes. As shown inFIG. 6, a storage section 4 electrically connected to the sheet sizedetecting section 3 is made to store eight bit combination patternscorresponding to sheet sizes beforehand. Each time the sheet sizedetecting section 3 detects a sheet, the combinations of the bits outputfrom the electric switches 30, 31 and 32 is compared with the bitcombinations patterns stored in the storage section 4, thereby detectingthe size of the sheet.

In the present embodiment, the bit generating section 19 provided withthe projected portion and the depressed portion 21 located at thepredetermined position, and the bit generating section 20 provided withthe projected portion, are arranged in parallel to the rack gear 14 andare movable in the direction in which the guides are movable. Theelectric switches 30 and 31 are located at positions to which the bitgenerating section 19 is movable. Likewise, the electric switch 32 islocated at a position to which the bit generating section 20 is movable.With this configuration, 3-bit information is obtained regarding thesize of the sheets stored in the manual insertion tray 11, and the 3-bitinformation can be compared with the bit combination patternscorresponding to the eight sheet sizes. Therefore, the controller of thecopying machine 1 can detect eight sheet sizes.

Unlike the prior art configuration, the present embodiment does not haveto employ three bit generating sections. That is to say, the presentembodiment uses two bit generating sections 19 and 20, and detection ofeight sheet sizes is enabled. Hence, the manual insertion tray 11 has adecreased width, and the sheet size detecting device is compact in sizeand does not occupy much space.

The bit generating sections 19 and 20 are arranged in two rows. Withthis configuration, a product error, such as a phase shift betweenadjacent rows, is prevented, and yet the structure is simple. It istherefore possible to provide a sheet size detecting device which isfabricated with high precision and at low cost.

In the first embodiment described above, the two bit generating sections19 and 20 have projected and depressed portions, and these portions aredetected by the electric switches 30, 31 and 32. However, the presentinvention is not limited to this. For example, a bit generating sectionmay be provided with a notch detectable by an electric switch.

Furthermore, it is not necessary to employ an electric switch for bitdetection. A sensor (e.g., a light sensor) may be arranged at apredetermined position, and the projected portion and the depressedportion or notch may be detected by checking whether light has passed orblocked.

(Second Embodiment)

The second embodiment of the present invention will now be described.Structural elements that are similar or correspond to those of the firstembodiment are denoted by the same reference numerals, and a detaileddescription of such structural elements will be omitted.

FIG. 7 is a schematic diagram showing how a sheet size is detectedaccording to the second embodiment of the present invention.

In the manual insertion tray 11 of the first embodiment, the rack gear15 is provided with the bit generating sections 19 and 20. The manualinsertion tray of the second embodiment does not employ this structure.In place of this structure, a pinion gear 16 rotatable on an axis ofrotation is provided with circular bit generating sections 41 and 43.Bit generating section 41 includes a projected portion extending in therotating direction of the pinion gear 16, and a depressed portion 42formed at the predetermined position of the projected portion. Bitgenerating section 43 is provided radially inward of bit generatingsection 41 and has a depressed portion extending in the rotatingdirection of the pinion gear 16.

The projected portions of the bit generating sections 41 and 43 arecovered with coatings that reflect light. Reflection type sensors 44 and45 are provided for bit generating section 41, and reflection typesensor 46 is provided for bit generating section 43. When the reflectiontype sensors 44, 45 and 46 detect the projected portions of the bitgenerating sections 41 and 43, they detect bits being generated.

With this configuration, the bit generating sections 41 and 43 rotatetogether with the pinion gear 16. The rotation of the bit generatingsection 41 allows detection of four bit combination patterns, namely,the patterns determined by whether or not reflection type sensor 44detects a bit and by whether or not reflection type sensor 45 detects abit. In addition, the rotation of the bit generating section 43 allowsdetection of two bit combination patterns, namely, the patternsdetermined by whether or not reflection type sensor 46 detects a bit.Hence, the manual insertion tray 11 of the second embodiment can detecteight sheet sizes, like the tray 11 of the first embodiment.

Rack gears 14 and 15 engaging with the pinion gear 16 extend in parallelto each other. Therefore, the diameter of the pinion gear 16 isdetermined in such a manner that the circumference of the pinion gear 16is equal to one half of the width required for detecting all sheetsizes. That is, the diameter of the pinion gear 16 is defined by(maximum of detectable sheet width)/2π.

According to the second embodiment, 3-bit information is obtainedregarding the size of the sheets stored in the manual insertion tray 11,and that 3-bit information can be compared with predetermined bitcombination patterns corresponding to the eight sheet sizes. Therefore,the controller of the copying machine can detect eight sheet sizes.

As described above, three bit generating sections are not required, asin the prior art. Since the second embodiment can detect eight sheetsizes by use of only two bit generating sections 41 and 43, and thediameter of the pinion gear is defined as (maximum of detectable sheetwidth)/2π, it is possible to provide a sheet size detecting device whosemanual insertion tray is compact in size and does not occupy much space.

The bit generating sections 19 and 20 are arranged in two concentricpatterns. With this configuration, a product error, such as a phaseshift between adjacent patterns, is prevented, and yet the structure issimple. It is therefore possible to provide a sheet size detectingdevice which is fabricated with high precision and at low cost.

In the second embodiment as well, the two bit generating sections 41 and43 may be provided with a notch detectable by a light sensor. Needlessto say, the bit detecting section may be an electric switch, as in thefirst embodiment.

The embodiments were described, referring to the case where the presentinvention is applied to the manual insertion tray 11 of a copyingmachine 1. The present invention is in no way limited to this. Forexample, it is applicable to a sheet size detecting device provided at apredetermined position of a sheet feed cassette to detect the size ofsheets stored therein.

Additional advantages and modifications will readily occur to thoseskilled in the art. Therefore, the invention in its broader aspects isnot limited to the specific details and representative embodiments shownand described herein. Accordingly, various modifications may be madewithout departing from the spirit or scope of the general inventiveconcept as defined by the appended claims and their equivalents.

1. A sheet size detecting device comprising: a tray in which sheets arestored; guides that can be adjusted in position in accordance with asize of the sheets stored in the tray; bit generation sections that aremoved in synchronism with movement of the guides; bit detecting meansfor detecting bits greater in number than the bit generating sections byat least one, based on movement of the bit generating sections; storagemeans for storing data on correspondence between combinations of bitsdetected by the bit detecting means and sizes of sheets which can bestored in the tray; and sheet size detecting means for detecting a sizeof sheets stored in the tray, based on the bits detected by the bitdetecting means and the data stored in the storage section.
 2. A sheetsize detecting device according to claim 1, wherein the bit generatingsections include projected and depressed portions that are moved in alongitudinal direction thereof, and the bit detecting means detects abit generated when the projected portion of the bit generating sectionsis moved to a predetermined position, turning on an electric switch. 3.A sheet size detecting device comprising: a tray in which sheets arestored; guides that can be adjusted in position in accordance with asize of the sheets stored in the tray; bit generation sections that arerotated on an axis perpendicular to a moving direction of the guides, insynchronism with movement of the guides; bit detecting means fordetecting bits based on rotation of the bit generating sections; storagemeans for storing data on correspondence between combinations of bitsdetected by the bit detecting means and sizes of sheets which can bestored in the tray; and sheet size detecting means for detecting a sizeof sheets stored in the tray, based on the bits detected by the bitdetecting means and the data stored in the storage section.
 4. A sheetsize detecting device according to claim 3, wherein the bit detectingmeans detects bits which are greater in number than the bit generatingsections by at least one.